Metal oxide production



Sept. 22, 1953 w. LANE METAL OXIDE PRODUCTION Filed Jan. 2, 1951 D u. w 2 H I s G m w OfiQi sm m M w v.( v 3 u 174 5 Z N vm m m H QMNMQF ;m m A u m 1 R H m U H COOLING FLUID Tl C1 INVENTOR Frank W. Lane A TTORNE 1 Patented Sept. 22, 1 953 METAL OXIDE PRODUCTION Frank W. Lane, Elkton, Md., assignor to E. I. du Pont de Nemours and Company, Wilmington, DeL, a corporation of Delaware Application January 2, 1951, Serial No. 203,871

12 Claims.

This invention relates to metal oxide manufacture through the decomposition of a volatile metal halide, and more particularly to the production of pigmentary titanium dioxide by the vapor phase oxidation of a titanium halide, especially titanium tetrachloride, under controlled conditions of reaction.

The vapor phase reaction of volatile metal halides at elevated temperatures with an oxygencontaining gas to produce a metal oxide is well ,known.

For example, the chlorides of titanium,

iron, aluminum, and the like can be reacted with versely affected. Where the reactor inlets are :arranged to insure such rapid mixing, a further difficulty arises due to formation upon such inlets of an objectionable, hard, crystalline oxide deposit. This deposit grows as the reaction pro- =ceeds to objectionably hinder the oxidation opera- :tion or eventually interrupts it altogether due to the apparatus plugging which it induces.

In :addition, objectionable oxide formation and deposition takes place on the internal walls of the reactor to constrict its cross section whereby the average retention time of reactants within the reactor is undesirably altered and modified so that the particle size of the resulting metal oxide reaction product is also adversely affected. As in the case of the reactor inlets, this wall deposition may eventually cause reactor plugging. This oxide deposition and apparatus plugging constitutes a major obstacle to a successful, continuous type of commercial operation for the production of metal oxides, and especially TiOz, by gas phase oxidation processes.

,Many proposals have been made for overcoming these difiiculties of prior vapor phase oxidation methods, including dilution of a reactant prior to use; maintenance of the reacting gas mixture out of contact with the hot surfaces of the reactor and "by means of an intervening inert gas stream; employment of oppositely disposed vapor inlets to the reactor; utilization of such reactant flow rates that the reaction products Will be swept past the halide reactant inlet; or

utilizing a relatively large reaction zone wherein reactant wall contact will be minimized. However, none of these proposals has proved satisfactory or effective for overcoming the difficulties above alluded to in prior vapor phase oxidation procedures.

It is among the objects of this invention to overcome the above and other disadvantages which characterize prior methods for oxidizing volatile metal halides, and particularly those which are encountered in titanium tetrachloride oxidations. It is among the particular objects of this invention to provide novel methods and means for accomplishing these objects as well as to provide novel and effective methods and means for preventing oxide-encrusted deposits from forming upon and adhering to the reaction zone inlets of a reactor employed in a volatile metal halide, and especially a TiCh oxidation; to provide a novel method for effecting the continuous production of high-quality metal oxides in desirably high, commercial yields, without encountering the objectionable interruptions or shutdowns due to apparatus plugging; to provide novel methods and means for effecting the rapid and thorough admixture and reaction in the gas phase of titanium tetrachloride and an oxidizing gas without the attendant difficulties which oxide deposition and scale formation would induce if allowed to occur; and to provide a novel and continuous type process for producing pigmentquality TiOz from a TiCl4 oxidation. Other objects and advantages of the invention will be apparent from the ensuing description and from the accompanying diagrammatic drawings where- Figure 1 is a vertical, sectional view of one useful form of apparatus in which the invention can be carried out; while Figure 2 is a vertical sectional view of a modified form of apparatus in which the invention can also be carried out.

These and other objects and advantages are obtainable in this invention which comprises vapor phase reacting a volatile metal halide with an oxidizing gas within a reaction zone, and during the reaction maintaining the reactant inlets to said zone at a temperature below that at which any substantial reaction will occur between said reactants but above the vaporization temperature of the halide reactant.

In a more specific embodiment, the invention comprises rapidly mixing and reacting titanium tetrachloride and a humidified oxidizing gas at temperatures ranging from about 9001200 C.

stance.

3 within a reaction zone, and throughout said reaction maintaining the discharge section of the walls of the reactant zone inlets at a temperature below 800 C., and preferably below 700 C., by continuously flowing a cooling fluid thereover but out of contact with said reactants.

As already noted, useful forms of apparatus in which the invention can be practiced are illustrated in the accompanying drawings. Such apparatus comprises vertical types of concentric jet or nozzle forms of reactors wherein a gaseous metal halide, particularly T1014, and anoxidizing gas such as humidified air can'bereadily and quickly mixed for desired reaction and oxidation of the halide. Preferably, these reactors are constructed of corrosion-resistant metal or alloys and are adapted to be lined, if desired; with aceramic or refractory material, such as silica, magnesia, porcelain, etc.,- also capable of withstanding relatively high' temperatures and the 1 ranged about the conduit I sothat a second fluid passage 5 is formed is an annular conduit '5' having' an inlet 8 and an orifice or outlet 9, the latter also discharging into the reaction zone 5. The external walls of conduit l facing those of conduit '5 in which conduit 5 is interposed are s'pacediy disposed from those of conduit l out at their point of lowermost descent into the reaction zone 5 can be conveniently united, as shown, to form outlet tip portions it. Similarly, the outer wall of conduit '5 adjacent to or contiguous with the reaction chamber wall ii is so arranged that it also partially extends into reaction zone 5 but in the form of a U bendit, the lower extremity of which bend terminates in a tip portionii. Suitably positionedwithin U-hend i" and the space formed between the opposing wall surfaces of the conduits l and l and extending for a relatively short distance over the exterior of said conduits from the up or lip portime is and M, respectively, is a. bank or plurality of tubular cooling coils H through the medium of which said tips and the outlet pas sages 4 and E] can be maintained in relatively c'o'ol condition throughout the oxidation reaction.

The bank or banks or cooling coils H can be made up of a suitable metal possessing .a relatively high thermal conductivity and adapted. to promote rapid heat transfer or dissipation, such as copper, silver, aluminum, or like metallic su The coils ii are in such numbers and so arranged about the orifice outlets t and e and especially about said lip portions that desired and efficient cooling thereof will be had without incurring any undue cooling or the preheated reactants prior to their introduction into the reaction zone after flowing through the passages 3 and 6. V

In operating such Fig. 1 device, a suitable cooling medium such as cold water is continuously flowed through the coils H whereby the lower parts of the walls of the conduits 3 and ii adjacent the outlets Q and It and the reaction chamber are maintained in relatively cool condition, e. g., at a temperature below 800 C., and preferabl below 700 C., in the instance of a T1014 oxidation. A volatile metal halide, such as tita nium tetrachloride, and an oxygen-containing gas, such as humidified air, preheated to tem peratures ranging from 800-1000 C. are then separately and continuously fed, at independently controlled rates or" flow, from suitable sources of supply (not shown) through the conduits 3 and drespectively, to discharge through the orifice outlets i and 5: into the reaction zone In consequence, desired mixture of the reactants takes place with reaction therebetween occurring. within the reaction zone at temperatures ranging, from 900-1200 C., with complete oxidation'of the halide being effected. The gaseous products of reaction formed in the zone 5 and containing the desired titanium dioxide product"; suspension are continuously withdrawn. from the reactor and subjected to aconventionalrecovery operation following their quick cooling or quenching to a temperature below 600 C., essential ina TiOapigment-production operationto prevent undesired. particle. size growth which wouldadversely afiectthe ultimate pigment properties and usefulness. of the final product. The productis thentreateo; in conven.- tional separatory apparatus including. collecting means such as settling chambers, filters, electrostatic precipitators, or the like. Prior to its use as a pigment, the TiOz. subjected to further treatment, including calcihation to efiect esidual chlorine removal. The residual gaseous products consisting of. a. halogen, andv any unreacted portions of the starting materials can. be concentrated, if desired, to provide a gas haw ing a higher proportion of halogen or, depending upon the reaction. conditions, they can be reemployed in the process, without recourse to such concentrating treatment.

To a clearer understanding of the invention, the following. specific examples are given, which are merely illustrative and not to be construed as in any wise limiting the invention:

Example I Titanium tetrachloride and dry oxygen, after being preheated to. 1609" C., were separately and continuously admitted in the molar ratio or 1:1 to a concentric jet reactor such as that shown in Fig. 1, the jet elements of which were constructed of fused silica. The reaction chamber was maintained at 196% C., and throughout the reaction water was continuously circulated through a copper coil disposed about the concentrically arranged inlets, said fluid being in sufficient quantity and in such state of coolness as to maintain the inner silica walls of the discharge section of the inlet jets at a. temperature of 700 C. The products of reaction, containing T102 in suspension, were discharged from the reaction chamber into a settling vessel asso. ciated with the reactor where most of the TiOz was retained, and were then passed through a glass cloth filter to an exhauset hood for recovery. After two hours of operation, the flow of reactants was discontinued, the reactor was cooled, disassembled, and its reactant inlet noz zles and interior inspected to determine whether oxide deposition thereon had taken place during the run. It was found that conversion of the 'IiCli to the oxide was substantially complete and that only a relatively small, insignificant amount of powdery TiOz deposit had formed on the tip iii of the central tubular conduit, and that such deposit was readily removable upon brushing, also that its presence was not of sufficient magnitude to interfere in any appreciable degree with the proper mixing and reaction of the reactants fed to the reactor.

After inspection, the apparatus was reassembled and the foregoing operation was repeated therein except that no water or other cooling fluid was circulated through the cooling coil during the reaction. After a short period of operation, the oxygen flow rate and to an even greater extent the titanium tetrachloride fiow rate were found to have become considerably reduced. After two hours, the operation was interrupted. The apparatus was then cooled, dismantled, and inspected. A hard encrustation or scale deposit was found to have formed on the tips I and II of the concentric jets through which the titanium tetrachloride and oxidizing gas reactant had been admitted. This deposit projected out for a distance of nearly two inches from the tip of the nozzles, gradually narrowing down at the end projecting into the reaction chamber to nearly close off the tubes. This deposit was very difficult to remove. In contrast to the substantially complete conversion obtained in an operation in which resort was had to cooled reactor inlets, only about 60% conversion of TiCl4 to the oxide was obtained in this instance, indicating clearly that deposit presence on the inlet nozzles objectionably interfered with proper reactant mixing and undesirably reduced and impaired unit capacity and efficiency by cutting down reactant flow rates.

In Figure 2 a modified form of apparatus is shown wherein rapid reactant mixing and reaction can be readily obtained. It comprises a water or other circulating fluid-cooled type of jet reactor I2, preferably constructed of nickel or other suitable corrosion-resistant metal or alloy adapted to be lined with a refractory material such as those referred to, and in which a plurality of open-ended tubular conduits or section members !3 and I4 are provided with an inlet l5 and an outlet [6. Said section members [3 and M are so arranged or disposed that they form a fluid passage I1, a mixing zone l8, and a reaction zone 19. The lower end portion or terminus 20 of member I3 and the upper end portion or terminus 2| of the member M are disposed in spaced, juxtaposed relationship from each other to form a relatively restricted, perimetric, transverse opening or elongated circumferential slot 22 for separately charging a fluid reactant into the conduit l1, mixing zone l8, and reaction zone I9, wherein it will be admixed for reaction with a suitable reactant adapted to be separately charged through the inlet I5 into said conduit, mixing zone and reaction zone. Fixedly or otherwise secured to and about said section members I3 and M- and extending a relatively short distance above and below and enclosing the inlet slot 22 is a manifold 23. The latter is provided with an inlet 24 and an internal chamber or fluid passage 25 which are in open communication with said slot 22 as well as the passage l1, mixing zone I8, and reaction zone 19. Said passage 25 of the manifold 23 surrounds said slot 22 and preferably is lined with silica or other corrosion-resistant material 26, and is formed by cooperatively arranging the section members 21 Y and 28 adapted to be bolted or otherwise suitably conduits 32 and 33, respectively, and outlet con-. 7 duits 34 and 35, respectively. 'A heat insulating material'such as powdered silica 36 is disposed between the silica chamber 26 and the walls of section members 21 and 28. r

In the operation of this Figure 2 device to produce, for example, a titanium dioxide pigment by vapor phase reacting, say, titanium tetrachloride with an oxidizing gas such as moisture-enriched air, a suitable cooling fluid such as water or oil is first charged and continuously conveyed during the reaction through inlets 32 and 33 and the ducts or channels 30 and 3|, to maintain the temperature of the inner metal wall 31 (which preferably consists of nickel) of the jet adjacent the mixing and reaction zones at a temperature from just above the condensation temperature of TiCh to just below the temperature where corrosion and resulting contamination of the pigment may objectionably occur, e. g., from about C. to 325 C." The oxidizing gas, at a temperature above 350 C., is then separately and continuously fed at a controlled rate into inlet l5 for charge through the passage I1. Simultaneously, gaseous titanium tetrachloride, at a temperature approximating that of the oxidizing gas, is separately and continuously conducted at a velocity ranging from about 15-40 times the mass velocity of the oxidizing gas, through manifold inlet 24 and passage 25 and discharged in the form of a relatively thin sheet or stream through the slot inlet 22 flowing radially from the outer periphery of passage I1 towards the center thereof and at right angles to and across the axis of flow of the oxidizing gas charging therethrough. Substantially instantaneous reactant mixing and reaction at temperatures ranging from about 9.00-1200 C. occurs on the two fluids coming together within the oxidation zone, and the reaction is substantially complete upon their passage downstream a short distance from the slot inlet 22. The reactants and resulting reaction products remain inthe oxidation zone for but arelatively short (from about .1-10 seconds) period which prevents undesired TiOz particle size growthand yet affords complete:-

conversionof the TiCli. The gaseous reaction products containing the TiOz in suspension are quickly cooled to below 600 C. on discharge from the oxidation zone, which quenching also prevents undesired particle size growth. In effecting cooling, cooled product gases from the system can be recirculated and directly commingled with the TiOz suspension as it issues from the oxidation zone, or, if preferred, cold, inert, finely divided refractory solids, such as silica orthe like, can be directly; dispersed in the suspension. The cooled T102 product is then conventionally recovered by. passing it into suitable settling chambers, cyclone separators, or the like. Such product consists of a uniformly small particle size pigment possessing desired high tinting strength, color, opacity, and other essential properties. It will be found adaptable for use in all types of pigment applications, including paints, enamels, finishes, or other coating composition formulations, as a delusterant for rayon or other artificial fibers and silks and as a colorant in printing inks, rubber, and the like.

Thefollowing is an illustrative example of an embodiment of the invention employing a Figure 2 reactor such as that just described:

Example II run were maintained incool condition and at about. 299 G; by continuously. fiowing suflicient,

.01 petro eum -;oi.1.-.thr0ueh. thecoo ing i ickets? 0. and 3|. The tubular passage -;l1 ,of,.the,,reactor had ,an internaL diameter. of 1 %I;- andr its; islet inlet, 22 was qg' g Of an inchdmwidth andextendedcompletely about the 1 periphery oi, said= passage.- Air containing .95% H2O. ,by ;vo1ume,-= preheated. to a .temperatureof ,8003; C,, ,was continuously. charged through passage I 1- :at a ,rate equivalent to 19 parts by weight of ,OaperhQun; vaporized- TiCl4 at :a temperature, of, 8655, C. was .simul-.

taneouslyied, at a continuous constant. flow rate,

of 100 .parts. bat-weight per :hour ,thro-ugnthe pass. sage 24. of manifoldjfl .andrdischarged into the passage I! through the. sl o t inlet ,22 in theform oi asheeted streamandacrossthe.air stream.be--..

ing concurrently conveyed .throughthat passaga. Substantially instantanecusrmixi-ng of the hu.-... midified air and T1014 reactants took-place atthe point of, theircmeeting, with substantially com.-.

plete mixing-andreaction. (at .a temperatureof,

1150, C occurrin downstreamsat a .point2" below. theslot inlet 22., Sincethegas streams. converge substantially immediately after entering themixing zone, the flowrates used provided.

anaverage retention time .of reactant gases and products-within the, reactor of.;.13 .of.la,.se cond. The TiOzsuspension issuin iromthe bottom .of.,.

the reactor ata-temperature of about 10.00? C.

was,.quenchedto 30.0,?. C.,within 2 seconds by d1.- rectly commingling. ,suffi'cient ,cold chlorine. gas

therewith; The,.TiOz productiwas thenseparated and recovered. ;fr'om-the cooled, .reaction.,..

products. incomenti'onal type ,filters and con;

S Sted of .a ..hig-h. gradegrutile,pigment. After. a run .oi3'hours during which no, diinculties were experienced in maintaining reactant new rates, and a. continuous vtype.otmoeration further reactants flow. was discontinued andthe apparatus was disassembledlfor inspection; No oxide scale deposition or build-jupwas found to, have occurred on. anypartjor the cooled inlet nozzle wallsor jet jtips andjadvantageously a substantially 100% TiCli. conversion was found .to have been obtained;

As a ,further illustration .of an operation utilizing the apparatus ,of. Fig; 1, theiollowing spe-- cific example is given;

Ferric chloridevaporand dry oxygen-gaaafterbeing preheated -to; 900 0;, were separately -ad-' mittedthrough water-cooled -fused-silica= nozzle inlets of the reactor-,the reaction zoneof which was held'at 900-CJ Thefiow of oxygen tothe apparatus was-adjustedto give-2,50 %-excess-over that required by the equation:

Water was continuously.circulated :during the re. action through the ecooling-rjackets tozmaintain the .inlet jet. walls. at a; temperature;- of about; 300? C. No difiicultieswere encountered inmain -n. tainingthegas .flowrratesas After running ior 90."

minutes-, further. flow: of reactants .was: discontinued. and. the apparatus" disassemb1edifor"in-.--

spection; Nor oxide,scalerdeposition'was found to;-; have; occurred. on? anyxparti of; the. cooled nozzle walls; or inlet :tips'; and;v at substantially; complete conversion WaSZ-fOUIIdgIQ' havebeen, efiected.

The apparatus- .was;;reassembled and the ;fore.-

going operation was repeated under identical conditions, except that no' cooling of the reactant inletswas, resortedto... Withingashort time after commencement.ofiItherun, difiic111ty. was eX..-. periencediin.maintainingthe. prescribed reactant,

titanium or-ferric chloride in pure state.

Although 'the inlet jets fandtheirassociated' flow .rates ,andthe gas now. was stopped com: pletely after 65 minutes of operation... Upondis: assembling ,the apparatus, t .was,,ioundilthat: its

reaction .zone, inlet .nozzles will be completely. plu edidue tothe presence of .a tightly adhering hard;,scaly oxidicdeposit upon, their discharge surfaces... R.en1oval..'of this} deposit from the nozzles (could. only be efiectecl. by acid. treatmentv which was. necessaryto avoid apparatus breakage.

Although. describedas applied to certain specifidembOdiments, it. willbe understood that the Thus, while inventionis,v not restricted thereto. particularly adaptable,to a continuous type of,

operation, it isapparent that the contemplated. oxidation-reaction can also be eifeotedinabatch or semir-continuous, manner. or. under; atmosp rid. superatmcspher c,. r. subatm sph r c. pressures, It'is .especiallyuseful for preparing 1 pigmentary TiOzjin rutile, or anatase crystalline formbparticularly through the decomposition of a titanium chloridesuc-h as Ti'Cli, at tempera tures in excess of 8041" C, and froimsay, 900 1350 C.; withianoxidizin gas, such as oxygen, oxygenenriched air, or with mixtures of oxygen-ens rich'ed air and an inertgas. Preferably, andto obtain an optimum form of TiO2 pigment, the oxidation is effected in accordance with the procedures of USS; Patent 2,488,439; issued November 15, 1949, wherein use is resorted to of an OXldizing gas containing 'small amounts (ran ng from .05=10%; and especially from .1-'5% byvolume, based on thetotal volume of reactants) of water vapor; Likewise, a co-oxidation procedure can be resorted'td-suchas in accordance with halides as well as the'vola'tile chlorides or halides o'f-other metals; or mixtures thereof; can be use provided;the halogen componentof r the halide employed has an atomic number greater than 9"(i.- e., chlorine; bromine; iodine). Among, ex-

amples-of suchadditionaliy-useful halides, those of zirconium, aluminum, chromium; vanadium; tin,- zine, tungsten, antimony, columbiu-m', tantalurnsete, can bemen-tioned: Tl1e--halide--reaetant canbe readily ..prepared.by, for example,

' vchlorinating. an-iorevorsothermetalliferous substance tcontaining themetal the. halide.=cf. -which is to-be prepared; Thus, titanium tetrachloride or; ferrie chloride.v can abenobtained by chlorina ing-t attitaniferous material suchas ilmenite, rutile, or aTiQz concentrate at from 600-1100"- C; 'inithe. presence of a solid orgaseousreducingagent suchas carbon, charcoal, coal; etc.-,

and-= thereafter-= fraetionaliy distilling the 1 mixed chlorides reaction product-to recover; the, desired parts where objectionable oxide scale deposition or build upis likely to occur are'preferably cooled by continuously flowing or circulating cold water asacooling medium throughone or more nickel or other type jacketing means or coilssurround= ingsuch inletasaid inlets, nozzles conduits' and their associated parts can'be COOlEdbYII'GSQlI-ililg to other fiuidjcoolingnnedia and can bacon-1 '9 structed of various other metals, alloys, or ceramic or refractory materials possessing corrosion resistance and heat conductivity characteristics. Thus, use is contemplated of any form of conventional cooling media including inorganic or organic heat exchange fluids. For instance, in addition to water, glycerin, alcohol, various well-known petroleum and lubricating oils, fused salts, steam, etc., can be employed. Similarly, in addition to nickel type coils or jacketing means, the latter can consist wholly or in part of silver, magnesium, platinum, aluminum, or stainless steel or corrosion-resistant alloys, etc.

Any desired vapor'inlet arrangement can be utilized in practicing the invention, provided it will afford the rapid and thorough mixing of the reactants which is being sought. These may comprise, as shown in the drawings, concentric type inlet tubes, or may consist of parallel, juxtaposed inlets, or non-parallel inlets so arranged that the gas streams meet at some point in the reactor. The halide and oxidizing gas may each be introduced into the reactor through separate nozzles, or a plurality of separately cooled inlets may be resorted to for one or both reactants. For instance, the oxidizing gas may be introduced into the reaction zone through a plurality of inlets angularly disposed in respect to each other and to the metal halide inlet whereby such gas will impinge on the halide stream from opposing sides and at a particular point within the reaction chamber.

The invention possesses the important advantage over attempts of prior processes to avoid encrusted oxide deposition on reactor inlets and surfaces in that oxidic deposition is obviated or minimized without any interference arising in the desired rapid mixing operation. Furthermore, a desired high conversion of the halide to the metal oxide of desired uniformly small particle size and other essential properties is bad Without any attendant shut-downs due to apparatus plugging from such deposition. As a result, the invention isoutstandingly useful in the production of high-quality anatase or rutile TiOg pigments, especially when employed in conjunction with the methods contemplated in the aforesaid H. H. Schaumann application, directed to the vapor phase decomposition of titanium tetrachloride under controlled oxidation conditions and in the presence of small quantities of water vapor or humidified air.

While I preferably effect jet cooling by continuously circulating liquid or vaporous type of tetrachloride oxidation using a fused silica jet,

heat exchange media through metal jackets or coils associated with the reactor inlet nozzles or jets, this can also be accomplished by spraying the liquid media onto and over the exterior surfaces of the inlet ducts or reactor Walls and out of contact with the reactants employed in the oxidation. Similarly, such media may be continuously flowed as a thin sheet or stream over the surfaces of the conductor metal or jacket and. opposite to the surfaces over which the reactant gases flow or pass. A heat exchange system can also be used wherein the cooling medium is recirculated after use and employed to partly preheat the cold halide and oxidizing gas reactants prior to use. Furthermore, a single reactant inlet or a portion of two or more thereof can be independently cooled to differing temperatures, whereby the reaction or condensation temperatures of the reactant being fed therethrough will be avoided,

I maintain the affected. inlets and reactor walls at temperatures below 800 C., and with a nickel jet at from about 137 C. to 325 C. In ferric chloride oxidations, I resort to reactor inlet and wail temperatures of not below 300 C. and preferably maintain temperatures ranging from about 300 C. to 500 C.

I claim as my invention:

1. A method for preventing metal oxide scale deposition and build-up upon the surfaces of inlets to a reactor employed in the vapor phase oxidation at temperatures above 700 C. of a volatile metal halide with an oxidizing gas which comprises during said oxidation flowing out of contact with the reactants a cooling fluid about said inlets to maintain them in cooled state and at a temperature substantially below said oxidation temperature but above the vaporization temperature of the halide reactant.

2. A method for overcoming oxide scale buildup upon the surfaces of inlets to a reaction zone in which a vaporized metal halide is reacted in the vapor phase and at temperatures above 700 C. with an oxygen-containing gas, comprising throughout the reaction flowing a cooling fluid about said inlets but out of contact with said reactants, said fluid being at such temperature and in such amount that the surfaces of said inlets are maintained at a temperature substantially below that at which said halide and oxidizing gas will react but above the temperature necessary to maintain the halide reactant in the vaporous state.

3. A method for overcoming oxide scale buildup within a reactor employed in the vapor phase oxidation at a temperature above 800 C. of a titanium halide with an oxygen-containing gas, which comprises throughout said oxidation continuously flowing a cooling medium about the reaction zone inlets and their associated reactor wall surfaces but out of contact with said reactants, said medium being at such temperature and in such amountthat said inlets and surfaces are maintained at a temperature substantially below that at which said halide and oxidizing gas will react but above the temperature necessary to maintain the halide reactant in vapor state.

4. A method for overcoming oxide build-up upon the surfaces of inlets to a reaction zone wherein vaporized titanium tetrachloride is reacted at a temperature above 800 C. with an oxidizing gas, comprising during said reaction flowing a cooling fluid about said inlets out of contact with said reactants to maintain the wall surfaces of said inlets at a temperature substantially below that at which said chloride and said oxidizing gas will react but above the temperature necessary to maintain said tetrachloride in the vapor state.

5. A method for overcoming oxide scale buildup upon the surfaces of the reaction zone inlets through which vaporized titanium tetrachloride and an oxidizing gas are separately introduced into said zone for reactionwhich comprises during said reactionmaintainingthe walls of said inlets with which said chloride and oxidizing gas come in contact during'their introduction into and reaction within said zone at a temperature 1 substantially below that at which interaction between said oxidizing gas and chloride will occur but above a temperature necessary to maintain said chloride in a vapor state by continuously flowing a cooling medium about said inlets out a of contact with said reactants.

6. A method for overcoming oxide scale buildup upon the surfaces of the reaction zone inlets through which vaporized ferric chloride and an oxidizing gas are separately introduced into said zone for reaction whichcomprises during said reaction maintaining the walls of said inlets with which said chloride and oxidizing gas come in contact during their-introduction into and re-- action within said zone at a temperature substantially belowthat-at which interaction between said oxidizing gas and chloride will occur but above a temperature necessary to maintain said chloride in avapor' state by continuously flowing a cooling medium about said inlets out of contact-with said reactants.

7. A process for overcoming oxide deposition and build-up upon the surfaces of inlets to a reaction zone throughwhich' vaporized titanium tetrachloride and an oxidizing gas preheated to a temperature of at :least 800 C. are separately passed for reaction within said zone attemperatures ranging from 900-1200 0., .whichcomprises maintaining thewalls of said inlets at a temperature below 800 C.-and that at -which interaction between said tetrachloride andoxidizing gas will occur but above the temperature at which said tetrachloride will vaporize by continuously flowing a cooling fluid about said inlets. but out of contact with the tetrachloride and oxidizing gas reactants.

8. A process" for preventing oxide deposition and build-up upon the-surfaces of inlets to a -reaction. zonewemployedi in reacting vaporized titanium tetrachloride and an oxidizing gas at temperatures ranging.from 900-1200 C. which comprises formingmsaid inlets and their associated reactorx-wall surfaces of a corrosion-resistant-metallic substanceland continuously flowing a fluid ccolingimedium out of direct contact with said reactants-lover at surface of said substance opposed torthessur-face'with which-said reactants comein contact during their introduction into and reaction within-said zone to maintain said latter surface at a temperature substantially below that at which chemical interaction between said tetrachloride and oxidizinggas will occur but above the temperature at which said tetrachloride will vaporize.

9. A process for preventing oxide scale deposition and build-up upon the surfaces of inlets to a reaction zone wherein titanium tetrachloride Number and an oxidizing gas are reacted attemperatures ranging-from 900-1200 C, following their separate introduction into saidzone which comprise forming said inlets of a corrosion-resistant metal a and throughout-the reaction circulating out of contact'with saidreactants a cooled heat exchange-fluid continuously over the surface of said inlets-=which areopposed to those which come in direct contact with said reactants, said fluid-being in" sufficient amount to maintain the walls of said inlets at a temperature above that atwhichthe vaporous TiCl4 will condense but not to exceed-800" C.,-and' below the temperature where corrosion of said metal will occur.

a 10. A process for minimizing oxide deposition and build-up upon the surfaces of inlets to a reaction zone through'which titanium tetrachloride and an oxidizing gas; preheated to temperatures-of at.. least-800 C.;-are separately conveyed for reaction, comprising forming said inlets of "metallic nickeland continuously circulating a fluid cooling mediumabout said inlets but out of contact with said reactants to maintain said metal at'a temperature not exceeding 325 C. but above C.

111A process for minimizing oxide deposition and build-up uponthe-suriaces of inlets to a reactionzone through-whichtitanium tetrachloride -and-an oxidizing gas, preheated to temperatures of at least- 800 C.,=are separately conveyed for "reaction, comprising forming said inlets of metallic nickel and continuously circulating oil about said inlets but out of contact with said reactantstomaintain said metal at a temperature passed to said zone-for reaction, at temperatures ranging from 700 C. to 1000 C., comprising forming said inlets ofa corrosion-resistant metal and continuously circulating out of contact with said reactants and over the surfaces of said metal opposite to those with'which said reactants come about 500 C.

;FIRANK W.v LANE,

liteferences: Cited; thetfile of this patent UN I'IED' STATES PATENTS Name Date 1 1,552,786 -Wescott Sept. 8, 1925 r 1,617,074 r Matlock Feb. 8, 1927 1,967,235 Ferkel July 24, 1934 2,155,119 .Ebner Apr. 18, 1939 2,394,633 Pechukas Feb. 12, 1946 2,445,691 Pechukas July 20, 19 18 

1. A MENTIONED FOR PREVENTING METAL OXIDE SCALE DEPOSITION AND BUILD-UP UPON THE SURFACES OF INLETS TO A REACTOR EMPLOYED IN THE VAPOR PHASE OXIDATION AT TEMPERATURES ABOVE 700* C. OF A VOLATILE METAL HALIDE WITH AN OXIDIZING GAS WHICH COMPRISES DURING SAID OXIDIZATING FLOWING OUT OF CONTACT WITH THE REACTANTS A COOLING FLUID ABOUT SAID INLETS TO MAINTAIN THEM IN COOLED STATE AND AT A TEMPERATURE SUBSTANTIALLY BELOW SAID OXIDATION TEMPERATURE BUT ABOVE THE VAPORIZATION TEMPERATURE OF THE HALIDE REACTANT. 